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Eukaryotic & Prokaryotic cells - Coggle Diagram
Eukaryotic & Prokaryotic cells
Prokaryotes
bacteria
organelles aren't membrane bound, and don't contain a nucleus
structures only found in Prokaryotes
mesosomas
infoldings of cell membrane that provide large surface area for attachment of enzymes involved in respiration - as they don't have mitochondria
loop of naked (not wound round histone protein) DNA that floats free in cytoplasm
peptidoglycan (murein) cell wall
pili
structures that can be found on the slime capsule
structures found in some Prokaryotes
protective wax capsule around the cell wall
plasmids
small loops of DNA, in addition to the main loop of DNA
flagella
different than eukaryotic undulipodia, its not built of microtubules
pili
small hair like projection that allow bacteria to adhere to host cells or each other & allow the passage of plasmid DNA from one cell to another
prokaryotic DNA
have a nucleiod within the cytoplasm & no nucleus
generally have 1 molecule of DNA, a chromosome which is supercoiled to make it more compact
the genes on the chromosome are grouped into operons (a number of genes are switched on or off at the same time)
may also contain plasmids (separate tiny loops of DNA carrying only a few genes) which occur throughout the cytoplasm
prokaryotic ribosomes
smaller than eukaryotic ribosomes
prokaryotic ribosomes = 70s
eukaryotic ribosomes = 80s
both types necessary for protein synthesis, but larger 80s are involved in formation of more complex proteins
Prokaryotic cell wall
made of peptidoglycan (aka murein)
complex polymer formed from amino acids & sugars
Prokaryotic flagella
thinner than eukaryotic equivalent & don't have the 9+2 arrangement.
energy to rate filament comes from process of chemiosmosis not ATP
attached to the cell membrane of a bacterium by a basal body & rotated by a molecular motor.
basal body attaches to the filament comprising it to the cell surface membrane. a molecular motor causes the hook to rotate giving the filament a whip like movement propelling the cell
<5μm
reproduce by binary fission
Eukaryotes
animals, plants, fungi, protists (or protoctists)
eukaryotes - multicellular, contains a nucleus, contains membrane bound organelles to keep organelles separate from rest of the cell, so its a discrete compartment
structures only found in Eukaryotes
cilia
membrane bound organelles
e.g. nucleus, nuclear membrane, nucleolus, mitochondria, Golgi apparatus, RER, SER, chloroplasts
vacuoles
linear DNA
cellulose/chitin cell walls
10μm
or yeast (unicellular)
reproduce by mitosis (asexual) & meiosis (sexual), or budding in yeast
membrane bound organelles
nucleus
function
houses nearly all a cells' genetic material
nuclear envelope - separates contents of nucleus from rest of cell & helps maintain shape
nuclear pores - enable larger substances (e.g. mRNA) to leave nucleus & substances (e.g. steroid hormones) to enter from cytoplasm)
nucleolus - produces RNA & ribosomes
chromatin - genetic material, when cell isn't dividing its spread out, when about to divide it condenses & coils tightly into chromosomes
nucleoplasm - stores DNA & is an isolated environment where gene regulation can take place
present in animal & plant cells
structure
contains chromatin consisting of DNA wound around histone proteins
contains nucleolus which makes & contains RNA, which is made into ribosomes (non-membrane bound)
surrounded by double membrane called nuclear envelope - has nuclear pores in it that let large molecules pass through into the nucleus - envelope contains nucleoplasm
visible under light microscope
mitochondria
structure
2-5μm long
spherical, rod shaped or branched
surrounded by 2 membranes - inner one folds inwards for large surface area - forming cristae, they project into a liquid called the matrix
inner membrane is coated in enzymes which catalyse the reaction of aerobic respiration to produce ATP
function
site of ATP production during aerobic respiration
self replicating so more can be made if cell needs more energy
they are abundant in cells where metabolic activity takes place (e.g. liver cells, sperm cells, synapses)
not visible under light microscope
present in animal & plant cells
rough endoplasmic reticulum (RER)
structure
system of membranes containing fluid-filled cavities (cisternae) that are continuous with the nuclear membrane
coated with ribosomes
function
intracellular transport system - the cisternae from channels for transporting substances from one area of a cell to another
provides large surface area for ribosomes which assemble amino acids into proteins
the RER transports proteins that were made on the attached ribosomes through the cisternae to the golgi apparatus for modification& packaging
present in animal & plant cells
not visible under light microscope
smooth endoplasmic reticulum (SER)
structure
system of membranes containing fluid-filled cavities (cisternae) that are continuous with the nuclear membrane
more tube shaped than the RER
no ribosomes on surface
function
contains enzymes that catalyse reactions involved with lipid metabolism such as;
synthesis of lipids/phospholipids needed by the cell
synthesis of cholesterol
synthesis of steroid hormones
its involved with absorption, synthesis & transport of lipids (from the gut)
present in animal cells
not visible under light microscope
golgi apparatus
structure
its a stack of membrane-bound, flattened sacs called cisternae
usually around 4-8 cisternae but can be up to 60 in single celled organisms
its single membreane is similar to that of a cell membrane in that it has 2 layers
3 primary components;
'cis' - cisternae nearest the endoplasmic reticulum
'Medial' - central layers of cisternae
'trans' cisternae farthest from the endoplasmic reticulum
secretory vesicles bring materials to & from the Golgi apparatus
function
receives proteins from the endoplasmic reticulum (ER) & modifies them by;
adding sugar molecules (making glycoproteins)
adding lipid molecules (making lipoproteins)
being folded into their 3D shape
makes lysosomes
it then packages the modified proteins into vesicles that are pinched off & then either;
stored in the cell
moved to the plasma membrane, to either be incorporated into it or be exported outside the cell
present in animal cells
not visible under light microscope
lysosome
structure
small spherical sacs, formed from the Golgi apparatus
surrounded by a single membrane
they are specialised vesicles
contain powerful hydrolytic (digestive) enzymes
abundant in phagocyte cells (e.g. neutrophils & macrophages - white blood cells that ingest & digest pathogens) The specialised lysosome (acrosome) in the head of sperm cells help it penetrate the egg by breaking down the material surrounding the egg
function
to keep powerful hydrolytic enzymes separate from the rest of the cell to prevent them damaging the rest of the cell
engulf old cell organelles & foreign matter, digest them, & return the digested components to the cell for use
present in animal cells
not visible under light microscope
cilia & undulipodia
structure
these are protrusions from the cell surface membrane
each contain microtubles
they are formed in the centrioles
in a cross section, they have an other membrane & a ring of 9 pairs of protein microtubules inside, with 2 microtubules in the middle - the '9+2' formation.
for microtubules see cytoskeleton
function
cilia on epithelial cells lining the airways beat & move mucus
nearly all cell types in the body have 1 cilium that acts as an antenna, it contains receptors & allows the cell to detect signals about its immediate environment
the only type of human cell to have an undulipodium (a longer cilium) is a sperm cell (spermatozoon), which enables it to swim
the microtubules contract which helps certain cells move by propelling the cell forwards
present in animal & plant cells
visible under light microscope
chloroplast
structure
4-10μm long
surrounded by a double membrane
inner membrane is continuous with stacks of flattened membrane sacs called thylakoids which give a large surface area
the thylakoids contain chlorophyll
each stack of thylakoids is called a granum (plural = grana)
grana are linked together by pieces of thylakoid membrane
the fluid filled matric is called the stroma
chloroplasts contain loops of DNA & starch grains
function
site of photosynthesis
1st stage - light energy is trapped by chlorophyll & used to make ATP, occurs in the grana. Water is also split to supply hydrogen ions
2nd stage - when hydrogen reduces CO2, using energy from ATP to make carbohydrates, occurs in the stroma
abundant in leaf cells, particularly the palisade mesophyll layer
present in plant cells
not visible under light microscope
vacuole
structure
permanent vacuoles only exist in plant cells. Animal cells can contain temporary vacuoles but they aren't common features
a vacuole is surrounded by a membrane called the tonoplast
it is filled with cell sap - a watery solution of different substances, including sugars, enzymes & pigments
function
the vacuole is important in keeping the cell firm & maintaining cell stability. When the vacuole is full of sap the cell is turgid
if all plant cells are turgid then this helps to support the plant, especially in non-woody plants
visible under light microscope
present in animal & plant cells
organelles without membranes
cellulose cell wall
structure
made up of 3 strata/layers;
2) primary cell wall
3) secondary cell wall
1) middle lamella
pectin rich & helps plant cells stick together
there are pores within the walls between cells called plasmodesmata these connect adjacent cells by their cytoplasm enabling the exchange of substances
they are permeable & allow solutions to pass through them
function
give cell support & structure
they withstand pressure & prevent cell from bursting when turgid
visible under light microscope
present in plant cells
ribosomes
structure
small, spherical - 20nm in diameter
made of ribosomal RNA (rRNA)
made in the nucleolus, as 2 separate subunits, which pass through the nuclear membrane into the cytoplasm & then combine (magnesium ions help bind the 2 subunits together)
some remain free in the cytoplasm & some attach to the RER
function
site of protein synthesis, which is where proteins are made. it acts as an assembly line to be used to make proteins from amino acids
ribosomes bound to the exterior of the RER are mainly synthesising proteins that'll be exported outside the cell
ribosomes floating free in the cytoplasm are mainly the site of assebly for proteins that will be used insde the cell
present in animal & plant cells
visible under light microscope
centrioles
structure
consist of 3 bundles of microtubules at right angles to each other
the microtubules are made up of tubulin subunits & are arranged to form a hollow cylinder
centrioles are self-replicating organelles made up of 9 bundles of microtubules
function
before a cell divides, the spindle, made of threads of tubulin forms from the centrioles
chromosomes are involved in the formation of cilia & undulipodia. before the cilia form, the centrioles multiply & line up beneath the cell surface - microtubules then sprout outwards from each centriole forming a cilium of undulipodium
present in animal cells & rarely, they're absent from higher plant cells - all eukaryotic cells have some sort of Microtubule Organising Centre 'MTOC' but neither fungi nor plant cells contain centrioles
not visible under light microscope
cytoskeleton
micro filaments
7nm in diameter
compostition
small solid strands made of the subunit of the protein actin. They are a polymer of actin
function
give support & mechanical strength (help resist tension)
keep the cell's shape
allow cell movement when the actin fibres contract, e.g. movement of cell membrane during phagocytosis & endocytosis
intermediate filament
10nm in diameter
composition
made of a variety of proteins
function
anchor the nucleus within the cytoplasm
extend between cells in some tissues, between special junctions, enabling cell - cell signalling & allowing cells to adhere to a basement membrane therefore stabilising tissues
microtubules
18-30nm in diameter
composition
straight, cylindrical microtubules, made of protein subunits called tubulin
function
also provide shape & support cells
help substances & organelles to move through the cytoplasm of a cell
they form the track along which motor proteins (dynein & kinesin) walk & drag organelles from one part of the cell to another
they form a spindle before a cell divides which enables chromosomes to be moved
microtubules also make up the cilia, undulipodia & centrioles
move vesicles from the endoplasmic reticulum to the Golgi apparatus
the assembly of microtubules & the movement of materials along them, requires energy from respiration
non-membrane bound. There's a network of fibres that run through the cytoplasm - this is the cytoskeleton, it has 3 types of fibre;
3) microtubules
1) microfilament
2) intermediate filaments
shared structures
cytoplasm
ribosomes
cell surface membrane (plasma membrane)
nucleic acids (RNA & DNA)
endosymbiosis
the hypothesised process where prokaryotes gave rise to the 1st eukaryotic cells - tries to explain the origins of eukaryotic cells (e.g. mitochondria & chloroplasts)
eukaryotic cells have a lot is the elements to be prokaryotic cells on their own (e.g. mitochondria - DNA, mitochondrial ribosomes, membrane bound. chloroplasts - DNA, ribosomes, membrane bound
these membrane bound organelles were once independent prokaryotic organisms that could release energy aerobically as well as precursors to modern eukaryotic cells but could only metabolise anaerobically.
the eukaryotic precursor would have engulfed the prokaryotic organism & they would have worked in symbiosis - the larger eukaryotic precursors provide nutrience & protection, the prokaryotic organism are able to better metabolise the nutrience & leverage O2 to release more energy
over time the symbiotic relation became so co-dependant on each other so the smaller prokaryotic organism couldn't operate on its own losing some of its DNA or having it incorporated into the DNA o the larger eukaryotic cell. The smaller prokaryotic organisms developing into what we now call modern eukaryotic cells
